This invention relates to a circuit of electrolytic cells suited with vertical electrodes for the electrolysis of aqueous solutions. More particularly, this invention relates to a circuit of electrolytic cells suited for the electrolysis of aqueous alkali metal chloride solutions.
Electrolytic cells arranged as a circuit have been used extensively for many years for the production of chlorine, chlorates, chlorites, caustic, hydrogen and other related chemicals. Over the years, such cells circuits have been developed to a degree whereby high operating efficiencies have been obtained, based on the electricity expended. Operating efficiencies include current, voltage and power. The most recent developments in electrolytic cells circuit have been in making improvements for increasing the production capacities of the individual cells while maintaining high operating efficiencies. This has been done to a large extent by modifying or redesigning the individual cells and increasing the current capacities at which the individual cells operate. The increased production capacities of the individual cells operating at higher current capacities provide higher production rates for given cell room floor areas and reduce capital investment and operating costs.
Circuit of electrolytic cells means a plurality of cells, which are electrically connected in series with a direct current power supply and which are arranged in one or more rows and are equipped with at least one portable jumper switch.
In general, the most recent developments in circuits of electrolytic cells have been towards larger cells which have high production capacities and which are designed to operate at high current capacities while maintaining high operating efficiencies. Within certain operating parameters, the higher the current capacity at which a cell is designed to operate, the higher is the production capacity of the cell. As the designed current capacity of a cell is increased, however, it is important that high operating efficiencies be maintained. Mere enlargement of the component parts of a cell designed to operate at low current capacity will not provide a cell which can be operated at high current capacity and still maintain high operating efficiencies. Numerous design improvements must be incorporated into a high current capacity cell so that high operating efficiencies can be maintained and high production capacity can be provided.
Circuits of electrolytic cells for making chlorine and caustic soda is of primary importance and will be used to exemplify our invention. Table I shows the development.
______________________________________ current KA 80.degree. 150 200 cell width m ca. 1.6 2.3 3.0 cell length m ca. 1.9 2.2 2.2 chlorine production 2.4 4.5 6.0 t/day ______________________________________
In the early prior art, chlor-alkali diaphragm cell circuits were designed to operate at the above mentioned current capacities having the shown production capacities.
Conventional circuits of electrolytic cells consist in a plurality of series-connected cells, normally arranged in two more rows. The cells are rated for a current up to about 150,000 Amps. The limited life time of certain cell parts, such as anodes, seperators respectively diaphragms, requires the removal of each cell from time to time and transportation of this cell to a workshop for the renewal of the spent or exhausted cell parts. Normally such cell circuits are equipped with one or more portable jumper switches for bypassing the electrical current around each incapacitated cell to the two adjacent cells, thus allowing steady operation of the cell circuit without any interruptions due to the incapacity of a cell.
In conventional cell circuits for bypassing a cell the jumper switch is positioned in an operation aisle in front of that cell and is electrically connected by means of busbars or cables to the cathode part of an adjacent cell and the anode part of the other adjacent cell. It is necessary to equip each cell with special means for the connection to the switch. By the positioning of the switch beside the cell row the current distribution in the adjacent cells is distubed.
As illustrated in FIG. -2- cell parts next to the operation aisle, where the switch is positioned, have to carry a higher electric load than normal, where as in the opposite cell parts the current is discharged. This uneven current distribution results in higher heat generation of overloaded cell parts, higher power consumption and lower current efficiency. Due to the fact of uneven current distribution in the switch-connected cells the length of the cells in conventional circuits is very limited. In conventional circuits of vertical-electrode cells the usual aspect ratio of cell length to cell width is about 2 or less. Regarding to this invention, cell length means the horizontal extension of the electrolytic chamber of the cell rectangular to the direction of the cell row and cell width means the horizontal extension of the electrolytic chamber of the cell in the direction of the cell row.
In conventional circuits of vertical electrode cells the jumper switch is located on the same level as the cells. For transportation of the incapacitated cell to the workshop the cell must be lifted by a crane over the switch or over the adjacent cells resulting in an enlarged construction height of the cell house building to accommodate the crane.
The above description of the prior art shows the development of chlor-alkali diaphragm cell circuits design to operate at higher current capacities with correspondingly higher production capacities. Chlor-alkali diaphragm cell circuits have now been developed which operate at high current capacities of about 150,000 amperes and upward to about 200,000 amperes with correspondingly higher production capacities while maintaining high operating efficiencies.
Nevertheless the circuits of electrolytic cells of the prior art are still subject to some disadvantages, which influence efficiencies, operating costs and capital investment and which prevent further increasing of cell current and production rates.